Most pipelines which carry fluids (e.g. petroleum, natural gas, two-phase fluids, etc.) need to be “pigged” at certain times. This is accomplished by inserting or “launching” a “pig” into the pipeline at a first point and allowing the fluids flowing through the pipeline to push the pig through the pipeline to a second point where it is “caught” and removed from the pipeline. As understood in the art, the term “pig” is used to generically describe any structure or device which freely moves through a pipeline to carry out a particular function.
Normally, pipeline pigs fall into two basic categories, i.e. non-intelligent pigs and intelligent pigs. Non-intelligent pigs are those which perform maintenance or operational functions, e.g. cleaning—such as scraping of solids, etc. from the interior of the pipe—; swabbing—such as removing liquids or gases from the pipeline—; batching—such as separating different fluids in the pipeline—, etc. Intelligent pigs are those which monitor and convey information about a particular condition or performance of the pipeline.
Certain pigs for large diameter gasoline pipelines are made of steel and rubber and sometimes foam and weigh in excess of 400 pounds. In the past, the industry has used manpower to insert these pigs. Typically this takes upwards of six men to do the job. In wet, muddy, rainy conditions, the use of manpower is not very effective and creates a safety issue. Other methods for inserting heavy pigs employ trucks to push the pig. The use of trucks, however, provides a source of ignition which also creates a safety issue.